Subamniotic hemorrhage
Subamniotic hemorrhage is considered a type of perigestational hemorrhage.
Pathology
Subamniotic hematomas are classical placental pathological lesions resulting from the rupture of chorionic vessels (allanto-chorionic vessels) close to the cord insertion.
A subamniotic hemorrhage is contained within amnion and chorion and thus extends anteriorly to placenta but is limited by the reflection of amnion on placental insertion site of the umbilical cord.
Most subamniotic hematomas are found after birth and result from excessive traction on the umbilical cord at delivery.
Radiographic features
Ultrasound
They may sonographically be detected as a solid mass (recent) or poorly reflective oval-shaped predominantly cystic mass (chronic), overlying the fetal plate of the placenta and covered in a thin membrane, adjacent to the cord insertion .
Differential diagnosis
- placental cyst
- placental cotyledon
- large umbilical cord cyst near the site of cord insertion
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